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docs(ab): native transport, Transport switch, known gaps and the type-check change

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Joseph Doherty
2026-10-07 19:12:32 -04:00
parent 9a576599e1
commit c7f7c940a8
5 changed files with 141 additions and 1 deletions
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docs/drivers/AbLegacy.md
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@@ -93,10 +93,39 @@ binds from the driver's `DriverConfig` JSON:
- **`Devices`** — one `AbLegacyDeviceOptions` per PLC (`HostAddress`, `PlcFamily`, optional `DeviceName`).
- **`Tags`** — pre-declared `AbLegacyTagDefinition` list (`Name`, `DeviceHostAddress`, `Address`, `DataType`, `Writable`, `WriteIdempotent`).
- **`Probe`** — connectivity-probe `Enabled` / `Interval` / `Timeout` / `ProbeAddress`.
- **`Transport`** — `Libplctag` (default) or `Native`; see [Transport](#transport-transport-option).
Full per-field descriptions live in the contracts assembly. The JSON skeleton is
reproduced in [docs/v2/driver-specs.md §4](../v2/driver-specs.md).
## Transport (`transport` option)
Same switch as AB CIP: `transport` = `Libplctag` (default) \| `Native`, a string (case-insensitive on read,
written as `"Libplctag"` / `"Native"`). `Native` is a managed PCCC-over-EtherNet/IP client
(`Driver.Ab.Transport`) and is **opt-in**; the default stays `Libplctag` pending the real-press gate and the
default flip. A change takes effect when the driver instance is recreated (a deploy that changes
`DriverConfig`); the AdminUI form has a **Transport** dropdown in the advanced section, and the driver logs
`transport=<X>` on every init. CLI: `--transport native|libplctag`. See
[AbCip.md §Transport](AbCip.md#transport-transport-option) for the shared behaviour (one pooled connection
per device, Forward Open throttle, routing).
Native routing: SLC500/MicroLogix/PLC-5 are direct; `logixpccc` uses UnconnectedSend and its SLC framing is
**unverified**.
### Native known gaps
- ⚠️ **Simulator-only.** PCCC reads and writes are verified against `ab_server` only. No real SLC/MicroLogix/
PLC-5 has been exercised, and the real-press gate (Task 21) is read-only and has not run yet.
- **PLC-5 native is N-file reads only.** Every other file type and all PLC-5 writes are refused, currently
surfacing as `BadCommunicationError` rather than `BadNotSupported` (#571). The planned default flip excludes
PLC-5 and `logixpccc`.
- Status-bit sub-element writes (e.g. `T4:0/DN`, `C5:0/DN`) are Unsupported natively (they would clobber the
control word); nothing goes on the wire. Sub-element arrays are Unsupported natively. L-file bit indexes
above 15 are allowed.
- **ST (string) file layout is uncaptured**, so the string byte order is unverified natively.
- Capture recipe for golden frames: `scripts/ab-capture/capture.sh` (see
[AbLegacy-Test-Fixture.md](AbLegacy-Test-Fixture.md)). Follow-up issues: #564 to #577.
## Testing
- **Unit tests** — `tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.AbLegacy.Tests/` cover the driver, the PCCC address parser, and the host-address parser via fake tag runtimes.